Blasting a cylinder head with fine grit.

I was chuffed to find a vapour blasting service that operates literally 5 mins stroll from my gaff.

My intention was to send the head off for ex thread repair and then when it's back get it blasted.

The blaster man asked if the head is painted. It is, with a silver powder. It looks ok, but is blotchy - a little more so after I've degreased it.

He recommends having it grit blasted before I send it off to remove any bits of paint and then when its back he will vapour blast it.

I mentioned that I was under the impression that grit blasting engine parts wasn't advisable (as per Norman White book), but he say's it's the way to go. He's been doing it a good while and does many engines without problem. He say's the grit is so fine (like egg timer fine) that it leaves nothing behind.

I figure it could be good as it will get the vapour treatment when it's back along with another scrubbing and power hose & air blow before assembly any how.

Am I leaning too heavily on NW words and over thinking it (I have a habit of doing that)?

Note. I'm not trying to get this bike concourse. Or even show. It's gonna be ridden, but I'd like it to be right.

Thoughts?

Definitely do not grit blast it or bead blast it

I wouldn't trust this guy. Trust the advice of NW. Soda blasting is the way to go for removal of varnish. Soda is soluble in water. Check this out:


- Knut

I'm so glad this forum exists, and I'm so glad I asked before I walked up to his place, head in hand (so to speak). I was literally just about to call him to make sure he was in.

And for once I'm so glad that occasionally over thinking things pays off.

Cheers guys.

First time ever I have heard a vapour blast guy turn away work well inside his equipment's capability. Go to someone else, regardless you will need to thoroughly clean it after as even with vapour blast grit will be left. I now clean with ultrasonic and no residues to worry about and a slightly less in your eyes finish closer to factory fresh.

Bonzo said:

I was chuffed to find a vapour blasting service that operates literally 5 mins stroll from my gaff.

My intention was to send the head off for ex thread repair and then when it's back get it blasted.

The blaster man asked if the head is painted. It is, with a silver powder. It looks ok, but is blotchy - a little more so after I've degreased it.

He recommends having it grit blasted before I send it off to remove any bits of paint and then when its back he will vapour blast it.

I mentioned that I was under the impression that grit blasting engine parts wasn't advisable (as per Norman White book), but he say's it's the way to go. He's been doing it a good while and does many engines without problem. He say's the grit is so fine (like egg timer fine) that it leaves nothing behind.

I figure it could be good as it will get the vapour treatment when it's back along with another scrubbing and power hose & air blow before assembly any how.

Am I leaning to heavily on NW words and over thinking it (I have a habit of doing that)?

Note. I'm not trying to get this bike concourse. Or even show. It's gonna be ridden, but I'd like it to be right.

Thoughts?

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If you were worried about grit getting in, you could have bolted some old valve covers on and put a nut and bolt through the valve guide , to seal up that side , all ways remove all oil and sludge , even a dry blast cabinet , can give you as good a finish as wet blasting , the trick is to drop all the old media and add brand new glass bead , it will give you a lovely clean sheen, it's the old dust in old media that makes a dull crappy finish . Then spend plenty of time cleaning with degreaser , water blaster, hot soap water compressed air with safety glasses, tap all threads and blow out and maybe use brake clean in the threads, clean clean clean .cheers P.S , glass bead comes in quite a few different grades , I'd imagine the factory had a shaker mat and people removing sand and flashing then probably blasted.

kommando said:

First time ever I have heard a vapour blast guy turn away work well inside his equipment's capability. Go to someone else, regardless you will need to thoroughly clean it after as even with vapour blast grit will be left. I now clean with ultrasonic and no residues to worry about and a slightly less in your eyes finish closer to factory fresh.

Click to expand...

I seek the 'slightly less in your eyes finish closer to factory fresh' of which you speak.

What size ultrasonic cleaner did you get to fit the CH in?

Bonzo said:

What size ultrasonic cleaner did you get to fit the CH in?

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Its a 30L tank, you can't get the whole head in but you can turn it over. An example of a crankcase 1/2 in for 20 mins.



and a TLS brakeplate which also needed to be turned over.



You can get different results with additives, my favourites with aluminium alloy are citric and/or oxalic acid with a drop of washing up liquid to reduce the surface tension. Phosphoric can work but you get a dark smut (Aluminium Phosphate) if you over do it, the citric will remove the smut but it takes a long time so best never to get it.

My local Vapor blast guy chemically strips the paint, then blasts.
Comes out very nice.
Specializes in M/C parts and is a rider.

This may sound weird, but when I had my cases split, I tried to clean up the outsides with some 000 and 0000 steel wool and acetone. Once I got started, I had such good results I couldn’t stop. Took a couple of days but it was almost therapeutic. I would never attempt that on a head.

I use walnut shells More aggressive then you would think. Leaves the aluminum looking more like factory then glass. What material is used for vapor blasting?

mean gene said:

I use walnut shells More aggressive then you would think. Leaves the aluminum looking more like factory then glass. What material is used for vapor blasting?

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When I was working I visited a local Porsche specialist and he was working on the inlet system of a v8 928. He was blasting the inlets, one closed port at a time, using walnut shells. Apparently the 928 would coke up its inlets if it wasn’t used hard enough. Much cheaper than the official Porsche way of engine out and heads off.

Flatspot said:

Much cheaper than the official Porsche way of engine out and heads off.

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I bet.

Use a liquid-based solution for removing paint, grease, etc. to prepare it for vapor blasting. Then vapor blast it and ultrasonic bath. This is a bit much for a garage mechanic such as myself without the means to purchase all this for use, but if the methods exist by cobbling several vendors together it is the best solution to your needs.

BTW I learned this from the BMW tribe who are absolutely RETENTIVE about their case's finish.

EDIT: A chroming shop often has a soak tank. I used this method locally to remove the factory coating from a pair of Fuchs rims but you want to be right by that tank and check the stripping regularly. Bring donuts, offer pizza lunch, or similar to gain access to the back and wear your work clothing.